Perpetual is battling to convince shareholders its $2.18 billion deal to sell its wealth management and corporate trust businesses to Kohlberg Kravis Roberts & Co will withstand scrutiny after admitting key aspects of the transaction such as its tax bill are unknown.

The agreement with the Wall Street private equity firm brings to a close a months-long strategic review of Perpetual’s business that drew interest from rival buyout firms, and culminated in the retirement of chief executive Rob Adams.